<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    
</body>
</html>
<script>
var divEle=document.createElement("div")
document.body.appendChild(divEle)
divEle.innerHTML="倒计时还有90分00秒"
var time=90*60;
    function yanchi(){
        time--;
        var minute=Math.floor(time/60)
        var second=time%60
        minute=minute<10?"0"+minute:minute
        second=second<10?"0"+second:second
        divEle.innerHTML = '倒计时还有'+minute+'分'+second+'秒'         
        console.log('yanchi');
        setTimeout(yanchi,1000);        
    }
    setTimeout(yanchi,1000)
</script>